[Theme: Twenty Fourteen] Grid – less padding or include post?

Another question about trying to make a child theme of Twenty-Fourteen.

There’s a lot of space between the two rows of the grid of featured posts.
Is this to do with padding? But if so, I’ve no idea where to find the code and therefore which file in the child theme to create or edit. Nor what code to use.

I’d be grateful to be pointed in the right direction.

Alternatively, and what would in fact be better for my site:
Can I show an excerpt of each featured post under the picture and post title? (In all that extra space!) A little bit of the post showing there would be very useful, giving that little bit more information so people are taken quickly to key information. Perfect would be if I could use MORE so I can define exactly how much excerpt is shown.

It would be fantastic if there is a way I can set that up. Possible?

Thank you.